I'm not saying you shouldn't call them out, in fact I'm 100% in favor of calling out BS. What I'm saying is to not shut down the conversation if the other side is willing to explain themselves or open to learning more.
One thing I absolutely loved about Reddit was joining communities where I was a minority and having a good faith discussion with someone I wasn't ideologically aligned with. A lot of times I got completely shut down, but sometimes I had really good discussions and better understood the other side's perspective.
So all I'm saying is you (and everyone here honestly) should seek to enable that kind of discussion instead of just stopping at the first sign of disagreement. Someone saying lolicon is as harmful as CP is probably just misinformed.
The end of polite and civil discussion
I have yet to see that, because I make a solid effort to have polite and civil discussion and I usually get it reciprocated.
If you're aggressive, you'll get aggressiveness back, but if you're inquisitive and polite, you'll likely get the same in return. Some people can't be reasoned with, but I have found that many are open to hearing other perspectives, provided I go out of my way to be polite.